Combustion chamber for gas turbine

ABSTRACT

Combustion chamber for a gas turbine, comprising two concentric sheet metal casings where the air enters and the compressed gases circulate in contra-current, chiefly notable in that the exterior casing, open at one end to receive the air, is closed at the other end by a cap provided with radial ribs which surround a central jet provided to inject an atomized combustible liquid, this jet opening onto one extremity of the interior casing where it is surrounded by profiled blades fixed slantwise to rotate the air, while this inner casing defines an expanded zone provided with a large number of small slots for the admission of the primary air of combustion, this expanded zone being extended by a short convergent part into which open lateral slots of relatively large diameter for the admission of second air after which the inner casing is continued up to the escape extremity by a divergent zone having wide lateral slots for the admission of coolant air, these slots being surrounded by a deflector fixed on the exterior of the inner shell with a view to prevent the formation of directly opposed currents of air admitted into the combustion chamber. This combustion chamber can, moreover, show the following characteristics envisaged separately or in combination: 1. An odd number of secondary air slots and an also odd number of slots for the mixing of coolant air. 2. Lateral slots for the secondary air are each provided with a tubular portion which is inclined towards the jet in the direction of the general axis of the chamber. 3. Two combustion chambers of this type are used, mounted parallel to one another in the same transverse plane with reference to the general axis of the turbine, their equilibration being assured by means of a by-pass channel which connects the two expanded zones of the two internal casings.

United States Patent Guillot 1 Mar. 21, 1972 [54] COMBUSTION CHAMBER FOR GAS TURBINE [72] Inventor: Jack Guillot, Bmanc-Mesni(Seine Saint- Denis), France Primary ExaminerMark M. Newman Assistant ExaminerW. E. Olsen Attorney-Sughrue, Rothwell, Mion, Zinn & Macpeak [5 7] ABSTRACT Combustion chamber for a gas turbine, comprising two concentric sheet metal casings where the air enters and the compressed gases circulate in contra-current, chiefly notable in that the exterior casing, open at one end to receive the air, is closed at the other end by a cap provided with radial ribs which surround a central jet provided to inject an atomized combustible liquid, this jet .opening onto one extremity of the interior casing where it is surrounded by profiled blades fixed slantwise to rotate the air, while this inner casing defines an expanded zone provided with a large number of small slots for the admission of the primary air of combustion, this expanded zone being extended by a short convergent part into which open lateral slots of relatively large diameter for the admission of second air after which the inner casing is continued up to the escape extremity by a divergent zone having wide lateral slots for the admission of coolant air, these slots being surrounded by a deflector fixed on the exterior of the inner shell with a view to prevent the formation of directly opposed currents of air admitted into the combustion chamber.

This combustion chamber can, moreover, show the following characteristics envisaged separately or in combination:

1. An odd number of secondary air slots and an also odd number of slots for the mixing of coolant air.

2. Lateral slots for the secondary air are each provided with a tubular portion which is inclined towards the jet in the direction of the general axis of the chamber.

3. Two combustion chambers of this type are used, mounted parallel to one another in the same transverse plane with reference to the general axis of the turbine, their equilibration being assured by means of a by-pass channel which connects the two expanded zones of the two internal casings.

8 Claims, 6 Drawing Figures COMBUSTION CHAMBER FOR GAS TURBINE The present invention relates to an improved combustion chamber for a gas turbine.

It is known that at the present time one of the principal conditions restricting the development of gas turbines, particularly for use in automotive vehicles, is the need to increase the thermal efficiency.

The present invention has for its object to provide a combustion chamber capable of increasing the thermal efficiency of a gas turbine, this combustion chamber being usable with a range of such turbines.

A combustion chamber for a gas turbine according to the invention comprises two concentric sheet metal casings in which the intake air and the compressed gases pass in contraflow. The exterior casing is open at one end to receive the intake air and is terminated at the other end by an upper cap provided with radial ribs which surround a central jet injecting an atomized combustible liquid, this jet opening into one extremity of the interior casing where it is surrounded by profiled blades fixed slantwise to rotate the air. This interior casing has an expanded zone provided with a large number of small holes for the admission of the primary air of combustion, this expanded zone being extended by a short convergent part having relatively large diameter lateral slots with tubes for the admission of secondary air, after which the internal casing is continued to its exhaust extremity by a divergent zone having wide lateral slots for the admission of coolant air. These slots are surrounded by an air deflector fixed on the extremity of the internal shell.

In a preferred embodiment of the invention, there is provided an odd number of secondary air ports and a number, also odd, of slots for the admission of coolant air. This prevents the formation of directly opposed air currents.

For certain applications, it is advantageous to pair together two combustion chambers. These two chambers are mounted parallel to one another, the equal action thereof being assured by a bypass channel connecting the combustion zones of the two internal casings. The two combustion chambers are disposed in the same transverse plane with respect to the main axis of the turbine, and they both connect with a common chamber surrounding the axis of the rotors, from whence the gas flows out axially through the fixed blades'ofa deflector to the high pressure rotor.

According to a further aspect of the invention, each combustion chamber is provided with a retractable sparking plug. This spark plug may be placed on a face of the expanded zone of the interior casing. A return spring maintains the spark plug outwards (i.e., extended into the zone) when the turbine is at rest, the pressure in the zone automatically retracting this spark plug as soon as the turbine begins to rotate. This retracting pressure is preferably made that ofthe compressor.

Finally, to ensure a rapid ignition when starting, and to assist the priming of the fuel pump, the jet is fed, through a valve controlled by an electromagnet coil, this valve controlling the direction, either towards the jet, or towards a return channel, of the fuel which it receives from a channel constantly maintained under pressure. This device prevents the formation of air traps upstream of the jet during the starting-up of the machine and the ignition of the fuel in the combustion chamber. The valve retains its position as soon as the chamber is fed with fuel, irrespective of the rate of the machine.

Reference should now be made to the accompanying drawings, wherein:

FIG. 1 is a fragmentary view showing the position of two combustion chambers according to the invention, located on the body ofa gas turbine,

FIG. 2 is a partial section along the line II-II ofFIG. 4,

FIG. 3 is an axial section along the line IIIIIl of FIG. 6 showing the arrangement of a retractable plug,

FIG. 4 is a transverse section of the turbine taken along the line IVIV ofFIG. 1,

FIG. 5 shows on an enlarged scale the injector shown in FIGS. 2 and 3,

FIG. 6 is a partial section taken along the line VI-Vl of FIG. 3.

FIG. 1 shows a part of a gas turbine which, forms part of a gas turbine prime mover. This device comprises chiefly those parts shown very schematically in FIG. 1, namely a rotor 2 of a centrifugal compressor, two combustion chambers 3 and a rotor of a high pressure turbine 4. The compressor 2 blows air into the chambers 3 from whence the hot gases emerge under pressure to cause rotation of the high pressure rotor 4. Downstream of the rotor 4, the turbine may comprise various known elements, such as one or more deflectors and low pressure rotors.

In the case of a gas turbine adapted to be used in an automotive vehicle, it is advantageous to utilize the arrangement shown in the drawings, having two parallel combustion chambers 3 situated in the same transverse plane with reference to the direction 5 defined by the shaft 6 of the turbine.

Each combustion chamber 3 comprises two concentric sheet iron casings, an outer casing 7 and an inner casing 8 (FIG; 4).

Each outer casing 7 is fixed directly on a housing 9 surrounding the shaft 6 of the turbine, this housing comprising an annular collector 10 receiving the air from the compressor 2.

The outer casing 7 is closed at its apex by a truncated cap 11 on which is fixed a fuel injector 12. This injector comprises a jet 13 which will be described later.

An interior sheet iron casing 8 has an apex l4 surrounding the jet 13 of the fuel injector. Downstream of the apex 14, the casing comprises a truncated cone 15, then an expanded cylindrical main combustion zone 16 and a convergent truncated cone l7 beyond which it is extended by a long divergent portion 18. This part terminates in a cylindrical coupling 19 which links up the combustion chamber with a collector 20 which directs the heated gas concentrically around the shaft 6, into a high pressure deflector 21.

FIGS. 2 and 3, show the shape of the inner casing 8, of which details are shown in FIG. 4.

The apex 14 of the inner casing 8 comprises fixed profiled blades 22 which are disposed around the jet 13, in such a way as to form a vortex from the passing air. To prevent eddy currents from forming at the moment when the discharge of air changes direction (Arrow 23), radial ribs 24 are spaced equidistantly around the apex l4 and fixed to the cone 11 and to the shell 7 of the exterior casing.

Immediately downstream of the vortex 22, the divergent portion 15 is bored with two series of small diameter holes 25. If the total diameter 26 of the combustion chamber 3 is of the order of millimeters, the divergent portion 15 is bored with two series of holes, each series comprising 12 holes each having a diameter of3 millimeters.

Similarly, the zone 16 has bored therein a large number of small holes. For the same size apparatus as referred to above, the expanded zone 16 has two series 27 of holes, each series containing 32 holes each of a diameter of 4 millimeters and being located on each side of a central series 28 made of 16 holes of a diameter of 4 millimeters.

The convergent portion 17 has an odd number of wide holes in each of which there is soldered a tubular length of pipe 29, the inner ends of which are tilted towards the top of the chamber 3. There are seven such tubes, each of a diameter of the order of 4 millimeters, spaced around the axis 30 of the chamber.

Immediately downstream of the convergent zone 17, in the divergent part 18, there is a series of holes 31, 20 in number, each having a diameter of 3 millimeters.

At its extremity, immediately in front of the cylindrical coupling 19, the divergent zone has large slots 32 distributed around the axis 30. These slots 32 are preferably odd in number, so as not to provide exactly opposed gas flows. These slots are seven in number and each has a width 33 of about 20 millimeters, and a height of 34 of 50 millimeters.

It should be understood that the preceding figures which concern the number and the dimensions of the various air inlets, have only been given by way of example, and can be modified at will, depending on the size of turbine.

Finally, around the apertures 32 of the divergent zone 18, there is a truncated cone shaped deflector 35 which widens upwards, and which is fixed on the collector 20 at the level of the cylindrical coupling 19.

To equalize the currents of hot gases produced by the two combustion chambers 3, and above all to ensure that both are always ignited, the expanded zones 16 of the internal casings 8 are connected by means of a cross-connecting channel 36 provided at its center with an expansion bellows 37. Thus, if the flame of one of the chambers is blown out momentarily, it is automatically re-lit from the other chamber.

FIG. shows the details of an injector 12 for a combustion chamber. This injector comprises a coil 38 of an electromagnet actuating a poppet valve 39. When the coil 38 is not energized, the valve 39 is located on a fixed seat 40 which it seals, preventing the jet 13 from receiving fuel under pressure from a feed channel 41. This fuel circulates through longitudinal channels 42 in the shell of the valve 39, and escapes by a return channel 43 (Arrow 44).

When the coil is energized, the valve 39 rises and comes to rest with its apex on a fixed seat 45, uncovering the seat 40. In consequence, the return channel 43 is blocked, and the jet 13 is fed with fuel from the channel 41.

It can therefore be seen that the valve 39 is either open or closed. The regulation of the rate of injection of the fuel into the chamber 3 by the jet 13 is effected by the control and regulating means of the turbine (not shown).

To complete the combustion chamber, a support cylinder 46 of a retractable sparking plug 47 is fixed to the external casing 7. When the plug is in the working position 47a (FIG. 6) it extends into the inner casing 8 at the level of the expanded zone 16.

This sparking plug comprises two electrodes (not shown), between which it is possible to produce a series of high tension electrical sparks. The spark plug 47 is integral with a piston 48 which slides in the interior of the support cylinder 46. This cylinder is divided into two chambers of which one contains a return spring 49 tending to extend the plug into the position 470; the other chamber 50 communicates with the interior of the combustion chamber. When fuel is burning, the pressure prevailing in the combustion chamber is sufficient to push the plug back into the retracted position 4717.

When not running, the pressure supplied by the compressor 2 is equal to that in the chamber 50 and, the spring 49 keeps the spark plug in the working position 47a. As soon as the turbine begins to rotate, the pressure in the combustion chamber increases. The plug is sparked to ignite the injected fuel, whereafter the pressure in the combustion chamber rises until the turbine is at full load. The pressure increase retracts the plug, which thereafter remains so, as long as combustion contmues.

The operation of the combustion chamber 3 is as follows: The air issuing from the collector l0 circulates between the casings 7 and 8 as indicated by the arrows 51 (FIG. 4). The deflector 35 prevents the air from impinging directly on the seven slots 32. Having reached the region of the cap 11, the current of air changes direction (Arrows 23) and passes into the vortex 22 where it is set in rotation to assist the atomization ofthe fuel provided by the jet 13. At this point, an amount of primary air which has penetrated into the inner casing 8 through the series of small holes 25, 27 and 28 is added thereto.

In the zone 17 where the fuel burns, the large tubed apertures provide a secondary air to complete the homogenation and burning of the mixture of air and fuel. The return of the secondary air (Arrows 54) is assisted by the tilt of the tubes 29.

Finally, the series of small holes 31 provides additional secondary air.

The primary air mixed with the fuel at the levels of the expanded zone 16 and the convergent zone 17, is the minimum quantity of air necessary to completely burn the fuel. The spent gases advance into the divergent zone 18 (Arrows 52) in contra-flow to the peripheral air (Arrows 51). At the level of the large apertures 32, the spent gases receive a portion of coolant air with which they are mixed (Arrows 53). The temperature of the mixture being thus brought to a desired level, the spent gas is'discharged into the collector 20 to activate the high pressure rotor 4 of the turbine.

What we claim is:

l. A combustion chamber for a gas turbine comprising inner and outer concentric casings wherein the inlet air travels in one direction within the inner casing, said outer casing being closed at one end with a plurality of radially extending ribs secured internally thereof and surrounding the corresponding end of said inner casing, fuel injection means secured in the closed end of said outer casing and disposed concentrically with respect to said inner and outer casings, said inner casing defining an annular opening about said fuel injection means, blade means disposed in said annular opening to form a vortex from the passing air, an expansion chamber formed by said inner casing downstream from said blade means and having a diameter larger than the diameter of said annular opening, a plurality of primary and secondary air openings formed through said expansion chamber, said inner casing diverging outwardly downstream from said expansion chamber, cooling slots extending through the diverging portion of said inner casing, and annular deflector means secured to said diverging portion downstream of said slots and substantially overlying said slots in spaced relation intermediate said casings to prevent the direct flow of inlet air into said cooling slots.

2. A combustion chamber as set forth in claim I wherein said secondary air openings are larger than and disposed downstream from said primary air openings in said expansion chamber, said secondary air inlet openings being odd in number and disposed circumferentially about said combustion chamber.

3. A combustion chamber as set forth in claim 1 further comprising additional air opening means formed in said diverging portion immediately downstream of said secondary air inlet openings which are smaller than said secondary air inlet openings.

4. A combustion chamber as set forth in claim 3 wherein said cooling air slots are disposed downstream of said additional air openings, said cooling slots being odd in number and disposed circumferentially about said diverging portion.

5. A combustion chamber as set forth in claim 1 wherein said annular deflector means has a truncated conical configuration with the smaller diameter portion being secured to said diverging portion of said inner casing downstream of said cooling slots.

6. A combustion chamber as set forth in claim 1 further comprising retractable spark plug means movable between a working position wherein said plug means extends into the inner casing and a retracted position wherein said plug means does not extend into said inner casing, spring means normally biasing said plug means into said working position and piston means responsive to increased pressures for retracting said plug means during self-sustained operation of the gas turbine.

7. A combustion chamber as set forth in claim 1 wherein said fuel injection means is comprised of a spray nozzle extending into said inner casing, feed channel means, return channel means, valve means for controlling the communication of said feed channel means with said spray nozzle said return channel means, and electromagnetic means for shifting said valve means to control the flow of fuel through said spray nozzle into said combustion chamber.

8. In a gas turbine engine of the type having a compressor means, turbine means, and a pair of combustion chambers intermediate said compressor means and said turbine means, the improvement comprising inner and outer concentric casings wherein the inlet air travels in one direction between said casings and said outlet gases travel in the opposite direction within the inner casing, said outer casing being closed at one end with a plurality of radially extending ribs secured internally thereof and surrounding the corresponding end of said inner casing, fuel injection means secured in the closed end of pansion chamber, said inner casing diverging outwardly downstream from said expansion chamber, cooling slots extending through the diverging portion of said inner casing, and annular deflector means secured to said diverging portion downstream of said slots and substantially overlying said slots in spaced relation intermediate said casings to prevent the direct flow of inlet air into said cooling slots. 

1. A combustion chamber for a gas turbine comprising inner and outer concentric casings wherein the inlet air travels in one direction within the inner casing, said outer casing being closed at one end with a plurality of radially extending ribs secured internally thereof and surrounding the corresponding end of said inner casing, fuel injection means secured in the closed end of said outer casing and disposed concentrically with respect to said inner and outer casings, said inner casing defining an annular opening about said fuel injection means, blade means disposed in said annular opening to form a vortex from the passing air, an expansiOn chamber formed by said inner casing downstream from said blade means and having a diameter larger than the diameter of said annular opening, a plurality of primary and secondary air openings formed through said expansion chamber, said inner casing diverging outwardly downstream from said expansion chamber, cooling slots extending through the diverging portion of said inner casing, and annular deflector means secured to said diverging portion downstream of said slots and substantially overlying said slots in spaced relation intermediate said casings to prevent the direct flow of inlet air into said cooling slots.
 2. A combustion chamber as set forth in claim 1 wherein said secondary air openings are larger than and disposed downstream from said primary air openings in said expansion chamber, said secondary air inlet openings being odd in number and disposed circumferentially about said combustion chamber.
 3. A combustion chamber as set forth in claim 1 further comprising additional air opening means formed in said diverging portion immediately downstream of said secondary air inlet openings which are smaller than said secondary air inlet openings.
 4. A combustion chamber as set forth in claim 3 wherein said cooling air slots are disposed downstream of said additional air openings, said cooling slots being odd in number and disposed circumferentially about said diverging portion.
 5. A combustion chamber as set forth in claim 1 wherein said annular deflector means has a truncated conical configuration with the smaller diameter portion being secured to said diverging portion of said inner casing downstream of said cooling slots.
 6. A combustion chamber as set forth in claim 1 further comprising retractable spark plug means movable between a working position wherein said plug means extends into the inner casing and a retracted position wherein said plug means does not extend into said inner casing, spring means normally biasing said plug means into said working position and piston means responsive to increased pressures for retracting said plug means during self-sustained operation of the gas turbine.
 7. A combustion chamber as set forth in claim 1 wherein said fuel injection means is comprised of a spray nozzle extending into said inner casing, feed channel means, return channel means, valve means for controlling the communication of said feed channel means with said spray nozzle said return channel means, and electromagnetic means for shifting said valve means to control the flow of fuel through said spray nozzle into said combustion chamber.
 8. In a gas turbine engine of the type having a compressor means, turbine means, and a pair of combustion chambers intermediate said compressor means and said turbine means, the improvement comprising inner and outer concentric casings wherein the inlet air travels in one direction between said casings and said outlet gases travel in the opposite direction within the inner casing, said outer casing being closed at one end with a plurality of radially extending ribs secured internally thereof and surrounding the corresponding end of said inner casing, fuel injection means secured in the closed end of said outer casing and disposed concentrically with respect to said inner and outer casings, said inner casing defining an annular opening about said fuel injection means, blade means disposed in said annular opening to form a vortex from the passing air, an expansion chamber formed by said inner casing downstream from said blade means and having a diameter larger than the diameter of said annular opening, a plurality of primary and secondary air openings formed through said expansion chamber, said inner casing diverging outwardly downstream from said expansion chamber, cooling slots extending through the diverging portion of said inner casing, and annular deflector means secured to said diverging portion downstream of said slots and substantially overlying said slots in spaced relation intermediate said casings to prevent the dIrect flow of inlet air into said cooling slots. 